I Have an 85 740 that set for a while about 1 year approx because it would not pass emmisions. After charging the batt i wen to crank it and vroom it started right up, and i noticed black smoke pouring from the exaust and thought it never did that before. I thought huh well if its going to blow ill blow it good so I took it for a spin ran like a champ after about 5 mins of touring arround it stopped smoking I scratched my head and said wtf ? i decided to check out the spark plugs and they were as black as the smoke pouring out of it super baked on carbon . it must have been depositing for a while due to the thikness of it. I guess it is running rich and this is why my NOx levels are up any solution to this problem ?